Magnetic disk drives are designed to attain ever increasing storage capacities while continuing to meet a rigid standard of error free operation and reliability. In addition, this must be accomplished within the constraints of the form factor for the disk size in use. The form factor is the limitation or standard that is recognized in the industry for the drive length, width and height. This standard, in practice, has been a defacto standard usually set by the dimensions selected for a flexible disk drive that is subsequently replaced by a hard disk drive. The hard disk file must fit into the same space occupied by the flexible disk drive and thus the dimensions are established, more by circumstance than by design.
In view of the size constraints, the only way in which the storage capacity can be increased is through an increase of the volumetric density of the drive. The combination of high areal density on the individual disk surface along with maximized disk density within the device envelope establish the potential for providing maximum storage within the drive.